New research shows that increasing the drainage depth can reduce the negative side effects of rice production in dry weather conditions. Researchers have observed that deep drainage increases the yield and nitrogen uptake in rice crops and reduces methane emissions. –Deep drainage is a way to increase the rice yield in a climate-smart way, but investments are needed in order to make it available to farmers, says Olive Tuyishime, PhD Student at the Department of Soil and Environment.
Rice production in Rwanda covers about 17,000 hectares of land and is important for the country’s food production. Flooded conditions keep the fields free from weeds and increase productivity, but it also increase denitrification, salinity, and methane emissions. Efficiently managing the water in the rice fields can improve the sustainability of rice production.
A new doctoral thesis focused on the effects of deep drainage in Rwandan rice fields has delivered promising results that can support rice production in arid and semi-arid climate zones.
-Our findings suggest that deep drainage performs better than shallow drainage in paddy rice fields in arid and semi-arid climate zones, as it enables a balance between maintaining water in the soil and having sufficient drain outflow to leach salts, reduce methane emissions and achieve high rice yield. In fact, deep drainage systems doubled the rice yields compared to shallow drainage systems says Olive Tuyishime.
Drainage: a balance act
The main role of drainage in Rwandan rice fields is to protect rice crops from excess soil water conditions during seedling and to improve accessibility for tillage operations and harvesting. However, excessive irrigation and high groundwater levels can lead to waterlogging and salinization. In these circumstances, proper drainage is needed to prevent waterlogging and salinisation. At the same time, excessive drainage can result in nutrient leaching, leading to decreased crop yield and adverse environmental effects. In other words, it can be a challenge to find the right balance of water management in the field. Recently, concerns have been raised about the potential negative impacts on the environment and potential threats to human health and biodiversity.
-We wanted to investigate how this situation could be improved by regulating drainage intensity (depth and frequency), under conventional shallow drainage depth of 60 centimetres and deep drainage depth of 120 centimetres, says Olive Tuyishime.
Irrigation and drainage go together
Throughout her research, Olive Tuyishime has worked closely with Rwandan rice farmers and seen at firsthand how her work has improved the situation. According to her, many of the farmers are facing increasing challenges due to climate change and water scarcity. Improved water management strategies such as deep drainage in semi-arid regions can help the farmers to a more resilient agriculture.
-The farmers were very excited about the impact our research has contributed to in their fields. However, it can be expensive to implement deep drainage. Despite considerable investments in irrigated agriculture in Rwanda, so far no sound investments have been made in drainage infrastructure. But proper drainage is just as important as irrigation.
Although Olive Tuyishime’s work has focused on Rwandan rice fields, her results are relevant in other regions with similar climate and conditions.
-The results can be useful to improve rice production in other parts of the world, which is essential regarding future population increase at a global level. It can bring forward benefits for both the farmer, the climate and the environment, whilst increasing the yields.
Read Olive Tuyishime's thesis: SLU publication database (SLUpub)